Development of supercritical water oxidation technology for application to hazardous waste treatment: An extreme case study

Abstract

Abstract Batch and continuous co-treatment of two typical hazardous wastes via supercritical water oxidation technology (SCWO) was investigated, that is, oil-based drill cuttings (OBDC) from a shale gas field and high-nickel-content electroplating sludge (Ni-EPS) from an electroplating factory. OBDC, an extreme representative of hazardous waste rich in organic materials, acts as an auxiliary fuel that provides heat from exothermic reactions during SCWO. The average reaction temperature in the continuous reactor increased from 378\xa0°C to 495\xa0°C. Ni-EPS, an extreme representative of hazardous waste rich in metals, acts as both a diluent and a catalyst. Metals in the Ni-EPS tend to form NiFe2O4, ZnFe2O4, and NiCr2O4 after SCWO treatment, and when OBDCs are present, they are transformed into metal oxides (MOx). All the metal oxides are in the form of nanoparticles and exhibit catalytic activity. Owing to the synergistic effect of high temperature and in-situ formation of nanocatalyst materials, the total organic carbon (TOC) in the effluents was as low as 8\xa0mg\xa0L−1, and the TOC removal efficiency (CRE) reached as high as 99.96%. This study provides an alternative process for the efficient and complete treatment of hazardous waste, and the obtained information will be helpful for commercialization of SCWO technology.